PLATE XX. 



Koeberlinia spinosa. 



Fig. 1. Tracheal tube bordering elongated pith cell, on margin of older 

 part of bundle. P, pith cell; Tr, tracheal tube. Longi-radial, x 636. 



Fig. 2. Elongated pith cells densely filled with finely granular food ma- 

 terial. Pits in walls omitted. P, pith; W, wood. Longi-section, x 

 283. 



Figs. 3, 4, 5, 6. Different views of tracheal tubes, all showing the cir- 

 cular opening at the end. 6 (a) Third partition in tube 6, showing 

 section of ring bordering aperture. These have become so completely 

 welded as to give the appearance of a continuous tube, as in 6. 

 Longi-section, x 400. Fig. 3 is the cavity outlined. 



Figs. 7, 8, 9. Sketches showing joining of ends of tracheids. Longi- 

 radial, x 400. 



Figs. 10, 11, 12. Various odd or malformed tracheids. Longi-radial, 

 X 283. 



Fig. 13. Regular rectangular tracheids. Longi-radial, x 283. 



Fig. 14. Single tracheid. Longi-radial, x 283. 



Fig. 15. Fiber-tracheid with small but numerous pits, x 283. 



Fig. 16. Wood fiber. Longi-section, x 283. 



